module.exports = function () {
    var _keyStr = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=";
    var scretKey = 'YXRvYmRlY29kZVVSSUNvbXBvbmVudA=='
    this.encodeKey = function(){
        let key = '',timeString = new Date().getTime().toString()
        for(let i = 0; i < scretKey.length; i ++){
            key += scretKey.charAt(i)
            if(i >= 4) key += timeString.charAt(i - 4)
        }
        return key
    }
    this.decodeKey = function(s){
        let timeString = '',reg = new RegExp('(' + scretKey.slice(0,4) + ')([a-zA-Z0-9]{26})(' + scretKey.slice(17,scretKey.length + 12) + ')')
        if(typeof s != 'string' || !reg.test(s)) return [false]
        let key = ''
        s.replace(reg, function($0,$1,$2,$3){
            for(let i = 0; i < $2.length; i ++) if(i % 2 == 1) timeString += $2.charAt(i)
            key = $1 + $2 + $3
            return ''
        })
        return [key,-(-timeString)]
    }
    this.encodeURI = function (s) {
        try {
            s = btoa(encodeURIComponent(s))
        } catch (e) {
            s = this.encode(encodeURIComponent(s))
            // return 'YXRvYmRlY29kZVVSSUNvbXBvbmVudA==' + Buffer.from(encodeURIComponent(s), 'utf-8').toString('base64')
        }
        let random = parseInt(Math.random() * (s.length - 1))
        s = s.slice(0,random) + this.encodeKey() + s.slice(random,s.length)
        return s
    }
    this.encodeTime = function(s){
        return this.decodeKey(s)[1]
    }
    this.canDecode = function (s) {
        return !!this.decodeKey(s)[0]
    }
    this.decodeURI = function (s) {
        let key = this.decodeKey(s)
        if(key[0]){
            if(new Date().getTime() - key[1] > 2 * 60 * 1000){
                throw 'decode time out'
            }
            // return decodeURIComponent(this.decode(s.replace(scretKey, '')))
            try {
                return decodeURIComponent(atob(s.replace(key[0], '')))
            } catch (e) {
                // return decodeURIComponent(Buffer.from(s.replace(scretKey, ''), 'base64').toString('utf8'))
                return decodeURIComponent(this.decode(s.replace(key[0], '')))
            }
        }else{
            throw 'decode error'
        }
    }
    this.encode = function (input) {
        var output = "";
        var chr1, chr2, chr3, enc1, enc2, enc3, enc4;
        var i = 0;
        input = _utf8_encode(input);
        while (i < input.length) {
            chr1 = input.charCodeAt(i++);
            chr2 = input.charCodeAt(i++);
            chr3 = input.charCodeAt(i++);
            enc1 = chr1 >> 2;
            enc2 = ((chr1 & 3) << 4) | (chr2 >> 4);
            enc3 = ((chr2 & 15) << 2) | (chr3 >> 6);
            enc4 = chr3 & 63;
            if (isNaN(chr2)) {
                enc3 = enc4 = 64;
            } else if (isNaN(chr3)) {
                enc4 = 64;
            }
            output = output +
                _keyStr.charAt(enc1) + _keyStr.charAt(enc2) +
                _keyStr.charAt(enc3) + _keyStr.charAt(enc4);
        }
        return output;
    }

    this.decode = function (input) {
        var output = "";
        var chr1, chr2, chr3;
        var enc1, enc2, enc3, enc4;
        var i = 0;
        input = input.replace(/[^A-Za-z0-9\+\/\=]/g, "");
        while (i < input.length) {
            enc1 = _keyStr.indexOf(input.charAt(i++));
            enc2 = _keyStr.indexOf(input.charAt(i++));
            enc3 = _keyStr.indexOf(input.charAt(i++));
            enc4 = _keyStr.indexOf(input.charAt(i++));
            chr1 = (enc1 << 2) | (enc2 >> 4);
            chr2 = ((enc2 & 15) << 4) | (enc3 >> 2);
            chr3 = ((enc3 & 3) << 6) | enc4;
            output = output + String.fromCharCode(chr1);
            if (enc3 != 64) {
                output = output + String.fromCharCode(chr2);
            }
            if (enc4 != 64) {
                output = output + String.fromCharCode(chr3);
            }
        }
        output = _utf8_decode(output);
        return output;
    }

    var _utf8_encode = function (string) {
        string = string.replace(/\r\n/g, "\n");
        var utftext = "";
        for (var n = 0; n < string.length; n++) {
            var c = string.charCodeAt(n);
            if (c < 128) {
                utftext += String.fromCharCode(c);
            } else if ((c > 127) && (c < 2048)) {
                utftext += String.fromCharCode((c >> 6) | 192);
                utfText += String.fromCharCode((c & 63) | 128);
            } else {
                utftext += String.fromCharCode((c >> 12) | 224);
                utftext += String.fromCharCode(((c >> 6) & 63) | 128);
                utftext += String.fromCharCode((c & 63) | 128);
            }
        }
        return utftext;
    }

    // private method for UTF-8 decoding  
    var _utf8_decode = function (utftext) {
        var string = "";
        var i = 0;
        var c = 0;
        var c1 = 0;
        var c2 = 0;
        while (i < utftext.length) {
            c = utftext.charCodeAt(i);
            if (c < 128) {
                string += String.fromCharCode(c);
                i++;
            } else if ((c > 191) && (c < 224)) {
                c1 = utftext.charCodeAt(i + 1);
                string += String.fromCharCode(((c & 31) << 6) | (c1 & 63));
                i += 2;
            } else {
                c1 = utftext.charCodeAt(i + 1);
                c2 = utftext.charCodeAt(i + 2);
                string += String.fromCharCode(((c & 15) << 12) | ((c1 & 63) << 6) | (c2 & 63));
                i += 3;
            }
        }
        return string;
    }
}  